The present invention relates to a sensor for automatic doors. In particular, the present invention concerns measures to conduct an object detection operation in a predetermined area without fail, thereby enhancing reliability of opening/closing action of automatic doors.
With respect to an automatic door which opens and closes along a track, an object detection range is usually set on an interior and an exterior of a doorway, and objects in a respective detection range are detected by an activation sensor. The activation sensor generally includes sensor mats, ultrasonic sensors and passive/active infrared sensors. On detecting entry of an object within the respective detection range, the activation sensor is turned on and operates to open the door.
In addition to the activation sensor, an auxiliary safety sensor is disposed in the vicinity of the track of the door, between interior and exterior detection ranges. As disclosed in Japanese Patent Laid-open Publication No. 2000-320243, the auxiliary safety sensor makes use of light beams (e.g. infrared rays). Typically, the auxiliary safety sensor can be classified into the three types.
A first type of auxiliary safety sensor is shown in FIGS. 6(A) and 6(B). FIG. 6(A) is a front view of an automatic door and FIG. 6(B) is a sectional view taken along line Bxe2x80x94B in FIG. 6(A). As illustrated, beam sensors are mounted on a pair of posts 62, 62 which stand on both sides of a doorway 61. Transmitters 63, 63 on one of the posts are positioned face to face with receivers 64, 64 on the other post. The structure in FIGS. 6(A) and 6(B) employs two beam sensors, each of which is composed of a transmitter 63 and a receiver 64. In each sensor, when a light beam is emitted from the transmitter 63 towards the receiver 64 and interrupted by a person or the like, the receiver 64 fails to receive the light beam. The sensor regards this condition as presence of an object near a track of doors 65. Based on this recognition, the auxiliary safety sensor holds the doors 65 open, even when the activation sensor is turned off.
A second type of auxiliary safety sensor is shown in FIGS. 7(A) and 7(B). FIG. 7(A) is a front view of an automatic door and FIG. 7(B) is a sectional view taken along line Bxe2x80x94B in FIG. 7(A). As illustrated, a transmitter 63 and a receiver 64 are mounted at an end of a first door 651, whereas mirrors 71, 71 are equipped at an end of a second door 652 in order to reflect light emitted from the transmitter 63 back to the receiver 64. Similar to the first type of auxiliary safety sensor, when a light beam is emitted from the transmitter 63 and interrupted by a person or the like, the receiver 64 fails to receive the light beam. The sensor regards this condition as presence of an object near a track of the doors 651, 652. Based on this recognition, the auxiliary safety sensor holds the doors 651, 652 open, even when the activation sensor is turned off. Such auxiliary safety sensor is disclosed, for example, in Japanese Patent Laid-open Publication No. H6-138253.
A third type of auxiliary safety sensor is shown in FIG. 8. An ultrasonic sensor 82 is built in a transom 81 above a doorway 61 and produces ultrasonic waves toward and around a track of doors 65. In FIG. 8, a detection area of the ultrasonic sensor 82 is defined by a dash-dotted line. According to this sensor, a sensor signal from the ultrasonic sensor 82 is considered valid only when the doors 65 are fully open. On the other hand, when the doors 65 are fully closed, or in a course of closing, any sensor signal from the ultrasonic sensor 82 is considered invalid. This principle prohibits the sensor 82 from wrongly detecting closing doors 65 as a person or other object, so that the doors 65 are not made to unnecessarily open.
However, these conventional sensors present various problems as mentioned below.
As for the first type of auxiliary safety sensor (FIGS. 6(A) and 6(B)), a detectable object is limited to an object which stands at or passes through a height and position where either pair of the transmitters 63, 63 and the receivers 64, 64 is mounted (i.e. at a height indicated by dash-dotted lines). In this case, the sensor fails to detect a small object located on the track (e.g. an object 66 depicted by an imaginary line i in FIG. 6). Consequently, the doors 65, 65 close as soon as the activation sensor is turned off, catching the object 66 between the doors 65, 65. As another problem, because the transmitters 63, 63 and the receivers 64, 64 are mounted on the posts 62, 62, it is impossible to direct light beams vertically above the track. Again, the sensor may fail to detect an object which lies on the track. In other words, if an object 67 is located at a position depicted by an imaginary line j in FIG. 6, the sensor cannot detect the object 67, which is high enough for the height and position of light beams, but which fails to block the light beams. Furthermore, installation of the transmitters 63, 63 and the receivers 64, 64 involves a complicated arrangement of wiring through an interior of the posts 62, 62.
The second type of auxiliary safety sensor (FIGS. 7(A) and 7(B)) can direct a light beam vertically above the track, thereby being capable of detecting an object which lies on the track. However, as with the first type of auxiliary safety sensor, a detectable object is limited to an object which stands at or passes through a height and position of either of the light beams. Referring to FIGS. 7(A) and 7(B), the sensor fails to detect a small object 66 laid on the track, as depicted by an imaginary line i. Moreover, installation of the second type of auxiliary safety sensor is more complex than that of the first type, because the transmitter 63 and the receiver 64 of the second type are mounted on the door 651 and need to have wiring arranged through an interior of the door 651.
The third type of auxiliary safety sensor (FIG. 8) solves the problem of arranging wiring through the interior of the posts 62, 62 or the doors 65, 65, and thus improves installation workability. However, this sensor has a different problem, because a signal from the ultrasonic sensor 82 is invalidated as soon as the doors 65, 65 start a closing action. Namely, once the doors 65, 65 start to close, it is impossible to detect a person coming from an area which is not covered by the ultrasonic sensor 82.
As mentioned above, none of the conventional sensors for automatic doors provides sufficient reliability in object detection. Therefore, there have been considerable demands for a sensor for automatic doors which can ensure satisfactory reliability with regard to object detection.
The present invention is made in view of the above problems. An object of the present invention is to provide a sensor for an automatic door which can ensure detection of an object in a predetermined area around the automatic door, thereby enhancing reliability of an opening/closing action of the automatic door.
In order to accomplish this object, the present invention intends to improve reliability of an object detection operation in the following manner. According to the present invention, image pickup means such as a CCD camera takes an image of a predetermined area around a door. From this image, a distance between the image pickup means and each object in the predetermined area is measured. Based on the measured distance, a sensor identifies presence or absence of an object which excludes a background object (e.g. a floor, a wall and the like) and the door.
A sensor for an automatic door according to a first aspect of the invention (hereinafter referrd to as Invention 1) is composed of image pickup means, distance measurement means, object identification means and output means. The image pickup means is capable of taking an image of a predetermined area around a door. The distance measurement means measures a distance between the image pickup means and each object that is in the predetermined area and observed in the image taken of the predetermined area, on receiving an output from the image pickup means. The object identification means identifies presence of an object which is neither a background object nor the door, on receiving an output from the distance measurement means.
Initially, each object for which a distance from the image pickup means is measured is identified either as a background object or as an object other than the background object, based on the measured distance. Then, each object other than the background object is identified either as the door or as an object other than the door. The output means outputs an object detection signal, on receiving an output from the object identification means. This object detection signal is produced, with a proviso that an object which is neither the background object nor the door is observed in the image taken of the predetermined area.
According to these features, once the image pickup means takes an image of the predetermined area around the door, the distance measurement means measures the distance between the image pickup means and each object observed in the image. Based on this information, the object identification means identifies the presence or absence of an object in the predetermined area excluding the background object and the door. If such object is present, the output means produces an object detection signal. This signal serves, for example, to keep the door in a fully open state. Thus, in order to identify the presence or absence of an object to be detected (e.g. a person), this sensor relies on the image taken of the predetermined area around the door. As a result, compared with beam sensors, the sensor of Invention 1 can have an extensive detectable range. Further, regarding identification of the presence or absence of the object, the sensor considers information except information relating to the door. Hence, even when the door is observed in the image taken by the image pickup means, the sensor ensures a reliable object detection operation, without mistaking the door for a person or the like.
A sensor for an automatic door according to a second aspect of the invention (hereinafter referred to as Invention 2) is composed of image pickup means, distance measurement means, floor detection means, object height/position detection means, door position detection means, door position identification means, judgement means and output means. The image taking means is capable of taking an image of a predetermined area which covers a track of a door. The distance measurement means measures a distance between the image pickup means and each object observed in the image taken of the predetermined area, on receiving an output from the image pickup means. The floor detection means detects a floor and a height and position of the floor, on receiving an output from the distance measurement means. At this stage, the floor is detected from any object for which a distance from the image pickup means is measured. The object height/position detection means detects a height and position of an object other than the floor, on receiving outputs from the distance measurement means and the floor detection means. It should be understood that the object other than the floor is an object which is observed in the image taken by the image pickup means covering the predetermined area, and which is located at a different height and position relative to the height and position of the floor. The door position detection means is capable of detecting whether the door is in an open position or a closed position along the track. The door position identification means identifies a position of the door in the image, on receiving an output from the door position detection means, based on the detected position of the door. The judgement means judges whether the object which is observed in the image taken of the predetermined area, and which is other than the floor, is the door or an object other than the door, on receiving outputs from the object height/position detection means and the door position identification means. The output means outputs an object detection signal, on receiving an output from the judgement means. The object detection signal is produced, with a proviso that the object which is neither the floor nor the door is observed in the image taken of the predetermined area.
Similar to Invention 1, these features realize a detection operation in the following manner. Once the image pickup means takes an image, the sensor of Invention 2 obtains information on a distance between the image pickup means and each object observed in the image. Based on this information, the sensor judges presence or absence of an object other-than the floor and the door. Therefore, the sensor can have an extensive detectable range and perform a reliable object detection operation, without mistaking the door for a person or the like. In particular, Invention 2 specifies an operation for distinguishing the floor (a background object) from any object other than the floor, and also specifies an operation for identifying a door position. These features serve to improve practicality of the sensor for an automatic door.
A sensor for an automatic door according to a third aspect of the invention (hereinafter referred to as Invention 3) features a specific operation of the output means for producing an object detection signal. In detail, the sensor of Invention 1 or Invention 2 is associated with door drive control means for controlling an open/close drive of the door along the track. In the sensor of Invention 3, the output means is arranged to be capable of outputting the object detection signal to the door drive control means, such that the object detection signal outputted to the door drive control means causes the door to open fully. These features prevent accidental closure of the door, while a person or the like is present near the track of the door. Eventually, the features of Invention 3 enhance reliability with regard to opening/closing action of the automatic door.
Sensors for automatic doors, according to fourth and fifth aspects of the invention (hereinafter referred to as Invention 4 and Invention 5, respectively), are featured by specific operations of the distance measurement means for measuring the distance between the image pickup means and each object in the predetermined area. With respect to any of Invention 1 to Invention 3, the sensor of Invention 4 employs image pickup means which has a plurality of image pickup elements. In the sensor of Invention 4, the distance measurement means is arranged to measure the distance to each object in the predetermined area, by stereo image processing which utilizes parallax of images taken by these image pickup elements.
Further, with respect to any of Invention 1 to Invention 3, the sensor of Invention 5 employs image pickup means which has a variable focus lens. In the sensor if Invention 5, the distance measurement means is arranged to measure the distance to each object, based on degree of focus on the object which is observed in the image taken by the image pickup means.
These features enable accurate measurement of the distance between the image pickup means and each object in the image taken by the image pickup means. In particular, the sensor of Invention 5 can simplify structure of the image pickup means, because the image pickup means associated therewith requires no more than one image pickup element.
Sensors for automatic doors, according to sixth and seventh aspects of the invention(hereinafter mentioned as Invention 6 and Invention 7, respectively), are featured by specific operations of the door position detection means for detecting the position of the door (i.e. open or closed). With respect to Invention 2, the sensor of Invention 6 is associated with door drive control means for controlling an open/close drive of the door along the track. This door drive control means produces an output signal corresponding to a position of the door. In the sensor of Invention 6, the door position detection means is arranged to be capable of receiving an output signal from the door drive control means, and to detect whether the door is in an open position or a closed position, based on the received output signal. By way of illustration, the door drive control means is arranged to output a pulse signal, wherein the number of pulses depends on the position of the door (i.e. open or closed). The door position detection means is arranged to receive the pulse signal and to detect whether the door is in the open position or the closed position, based on the number of pulses.
Also with respect to Invention 2, the sensor of Invention 7 arranges the door position detection means to detect whether the door is in an open position or a closed position, based on the image taken by the image pickup means. For example, a door position (i.e. open or closed) is detected in accordance with a position and angle of an edge of the door in the image taken by the image pickup means.
These features enable accurate detection of the door position (i.e. open or closed). In particular, the sensor of Invention 7 can simplify structure of the automatic door as a whole, by omitting a sensor or the like specially arranged to detect whether the door is in the open position or the closed position.